Do you need a modem and a router for internet with a new ISP?

When you sign up for a new Internet service, you may be presented with a modem and router, or a device that does both. Do you really need a modem? and a router to use the internet? It’s time to clear up some misconceptions.

Clarifying the meaning of “modem”

The word “modem” is short for modulator/demodulator. It refers to a device used for dial-up Internet, where data is sent over the same copper phone lines that voice calls use.

The modem takes the ones and zeros representing the data packets sent over the internet and converts them into sound frequencies over copper wire. It also does the reverse, listening to the sounds coming from the internet and converting them back into binary code.

Modern modems used with DSL, fiber, cable and mobile data are not modems in the original sense of the word. However, what they have in common is converting digital data from the computer to the format of the transmission system, for example converting electrical impulses into the light pulses used in fiber optics.

The most important thing to know is that a modem is a device that connects you to the greater internet. It is the transition point from your home LAN (Local Area Network) to the WAN (Wide Area Network).

What is a “router”?

Network data enters your home or business through the modem. Yet it is a router that directs network traffic to each individual device, both between each other on the internal network and between those devices and the Internet.

The work of a router is complicated and these devices are basically dedicated computers with their own CPU, memory and operating system. You can connect network switches, PCs, smartphones, and any other Wi-Fi or Ethernet device to a router, and it will figure out where to send each packet. Routers, at least more expensive ones, can also run network applications. For example, it can act as a VPN device or manage networked storage.

Most routers offer at least four Ethernet ports and Wi-Fi, which can connect and manage tens or even hundreds of devices. Unless you literally only have one device that you want to connect to the Internet via a modem, you’ll want some sort of router.

Fiber vs DSL vs Cable vs Cellular Modems

While many devices share the “modem” label, they are not interchangeable. Most home broadband modems have an Ethernet port on your end of the connection, but they’re radically different on the Internet side. Fiber optic modems connect to a fiber optic link, DSL connects to copper telephone cables, cable modems connect to coaxial TV cables, and cellular modems use microwave radio signals.

So, in this context, the answer to “do I need a modem?” is “yes” if you are moving from one type of connection to another. For example, your old DSL modem will not work with fiber or cable connections.

Sometimes the modem is already there

If you move into an apartment building or house where there is a “fiber optic” connection, you can find a plain old Ethernet port, which you can plug into any router with a “WAN” Ethernet port. In other words, you don’t need to buy a modem because one is already installed.

This is especially true in the case of fiber. People think of “fiber optic modems” as Ethernet routers that connect to ONTs (Optical Network Terminals). That is the device that converts electrical Ethernet signals into pulses of light.

So fiber routers are just regular routers, but they usually support faster Ethernet standards. If you have gigabit fiber but connect a router that only supports 100 Mbps Ethernet, you will lose 90% of the full speed of your internet connection!

If there’s a device with only one or two Ethernet ports and no Wi-Fi, you’re probably looking at a modem that you can plug in a router to extend functionality.

The pros and cons of all-in-one devices

If you need a modem for your type of connection, since one is not included in the ISP plan or was not yet installed, you can purchase a combination device that contains both a modem for your broadband type and an Ethernet and Wi-Fi router. contains.

You only need such an all-in-one unit if you don’t already have a modem, but if you do need one, there are a few pros (and drawbacks) to going for one device that does it all.

On the positive side of the equation:

  • It is usually cheaper than two separate devices.
  • You only have to deal with one uniform installation process.
  • Troubleshooting is easier because fewer individual devices are involved.

On the not so positive side of the equation:

  • If the device goes down, you won’t have internet. With a separate modem you can still connect at least one device in no time.
  • The router part of the device may not be very good, stable or support advanced features like network storage or VPNs.

Another big problem with using a combination device has to do with the Wi-Fi footprint. These days, most users want WiFi to cover their entire home, and unless you live in a small apartment, a single router probably won’t cut it, which is one reason you might want to have a separate modem and router.

Rent an all-in-one device from your ISP

Many ISPs offer an all-in-one device that includes both a router and modem for your particular connection type. If you can’t afford to buy your own solution and it doesn’t represent a significant additional cost to your monthly rental, it won’t hurt to use these devices for a while.

However, ISPs tend to bundle the cheapest devices they can with their services. If it’s a turnkey router, you can read reviews about it, but sometimes these devices get modified and renamed, making it hard to know if they’re any good.

Also, keep in mind that some ISPs allow you to keep the router once it’s paid off, while others only offer a pure rental, meaning you’ll have to return the device when you end your subscription. In general, it is better to choose the rent-to-own option if it is available.

Using a modem with a separate router

Whether you already have a modem and still need a router or whether you need to buy both items, there are definite benefits to separating the two.

For starters, you can focus your budget on your router solution and just buy a basic modem. As long as the modem works at the speed your connection provides, there isn’t much to look for in these devices.

If you have a big house and want to spread the WiFi, you can use a mesh WiFi router. This is preferred, but you can also use powerline ethernet and wifi extenders. If you’re using a single router, you have the option of using Wi-Fi repeaters, but they come with serious speed and latency penalties, and we can’t recommend them anymore these days.

You also have the option of connecting additional access points (or an old router set to access point mode) to extend the range of your network without compromising speed. This is a good option if you want to save money compared to a mesh router solution or if you already have a few old routers in your closet.


Let’s summarize it all to the main points:

  • Strictly speaking, you only need a modem to connect to the Internet.
  • Modems generally only offer a single Ethernet port and no Wi-Fi.
  • You need a router to connect all devices in the house to the modem.
  • You can buy a modem and router combo device, but they have compromises.
  • Mesh Network Routers or powerline extenders are superior to WiFi repeaters and plug directly into a modem’s Ethernet port. This makes this a better choice than a combined modem-router unit for large homes.

By now you should have a clear understanding of the different tasks modems and routers do, that you should have for your needs, and the different ways these devices can be combined.

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